CN1075081C - Expandable polyester branched with ethylene copolymer - Google Patents

Abstract

A class of branched polyester compositions having an intrinsic viscosity of at least about 0.7 deciliter per gram and a melt viscosity sufficiently high to be foamable during an extrusion or molding process is disclosed. Such branched polyesters can be readily foamed with a variety of blowing agents to form low density shaped articles, films and sheets. Such branched polyesters comprise from about 80 to about 99.9 weight percent of a polyester and from about 0.1 to about 20 weight percent of an ethylene copolymer; the ethylene copolymer contains repeating units of ethylene and selected from the group consisting of acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate, and vinyl alcohol monomers. The polyester comprises a repeating unit composed of about 75 to 100 mol% of a dibasic acid having 6 to 40 carbon atoms and 0 to about 25 mol% of a modifying dibasic acid, and a repeating unit composed of about 75 to 100 mol% of a dibasic acid having 2 to 10 carbon atoms, 0 to about 25 mol% of a modifying dibasic acid, and 0 to about 25 mol% of a modifying compound selected from the group consisting of aminoalcohols, diamines, and lactams.

Description

Expandable polyester branched with ethylene copolymer

field of invention

This invention relates to high molecular weight polyester compositions having high melt viscosity and high melt strength which can be foamed with a wide range of blowing agents. More particularly, the present invention relates to polyesters containing ethylene copolymer branching agents, and foamed articles produced from such polyesters,

Background of the invention

Many polymeric materials are foamed to provide low density articles such as films, cups, food trays, trim strips and furniture parts. For example, polystyrene pellets containing low-boiling hydrocarbons such as pentane are foamed into lightweight foam cups for hot beverages such as coffee, tea and hot chocolate drinks. Polypropylene can be extruded in the presence of blowing agents such as nitrogen or carbon dioxide gas to form decorative films and packaging tapes. Polypropylene can also be injection molded in the presence of such blowing agents into lightweight furniture parts such as table legs, and can also be molded into lightweight chairs.

Polyesters such as polyethylene terephthalate have a much higher density than other polymers (eg, about 1.3 g/ ^cm3 ). Therefore, it is desirable to foam polyester materials in order to reduce their weight for the manufacture of molded parts, films, sheets and food trays. The insulating properties of such foamed products are also superior to those of unfoamed products. However, such polyester materials are difficult to foam because of the low melt viscosity and melt strength of typical polyethylene terephthalate and related polyester polymers. The low melt viscosity and low melt strength of polyesters is a problem because the polymer melt cannot always adequately retain the bubbles of the blowing gas during the molding or extrusion process. Therefore, it would be desirable to be able to provide polyester polymers which can be foamed by conventional foaming systems.

One method of providing high melt viscosity polyesters involves treating preformed polyesters with polyfunctional carboxylic acid or polyol monomeric materials to form branched polyesters. Such compositions are disclosed in US Pat. Branching agents used include tri- and tetra-carboxylic acids and anhydrides such as trimellitic acid, pyromellitic acid and pyromellitic dianhydride or polyalcohols such as Methylolpropane and Pentaerythylpropanol. Such monomeric branching agents are capable of increasing polyester melt viscosity and melt strength, but their use is often disadvantageous. A common method of adding a branching agent is to melt the polyester in the extruder and add the branching agent to the melt in the extruder barrel. However, it is difficult to control the amount of branching agent used, and it is also difficult to mix and react well before the melt exits the die.

In order to solve the above problems and provide polyesters with sufficient melt strength to be easily foamed and excellent foaming properties, US Patent 5,399,595 to Sublett discloses the following method, which is basically composed of terephthalic acid or naphthalene dicarboxylic acid and aliphatic A small amount of dicarboxylic acid sulfomonomer such as sulfoisophthalic acid (sulfoisophthalic acid) is added to the polyester composition composed of repeating units of cycloaliphatic dihydric alcohol. Such foamable polyesters are prepared by combining melt-phase polymerization and solid-state polymerization to obtain easily foamable polyester compositions.

Summary of the invention

In order to solve the above-mentioned problems of the prior art, the inventors of the present invention have provided a branched polyester having increased melt viscosity and melt strength for producing foamed articles with excellent foaming properties, providing the characteristic Foamed articles of branched polyester having a viscosity of at least 0.7 dl/g and a melt viscosity high enough to be foamed during an extrusion or molding process. The branched polyester contains:

(A) A polyester comprising:

(1) repeating units derived from about 75 to 100 mole percent dibasic acids containing 6 to 40 carbon atoms and 0 to about 25 mole percent modified dibasic acids, and

(2) by about 75～100% mole containing the dibasic alcohol of 2～10 carbon atoms, 0～about 25% mole modified dibasic alcohol and 0～about 25% mole be selected from aminoalcohol, diamine and lactam The repeating unit obtained by modifying the compound; the % mole is based on (1) being 100% mole and (2) being 100% mole;

(B) From about 0.1% to about 20% by weight of the combined weight of (A) and (B) containing ethylene and selected from the group consisting of acrylic acid, methacrylic acid, alkyl acrylates, alkyl methacrylates and vinyl alcohol Ethylene copolymers consisting of repeating units of monomers.

According to another embodiment of the present invention, a kind of method comprising the preparation of branched polyester foam product of following operation is provided:

(a) Preparation of polyesters comprising repeat units (1) and (2):

(1) repeating units derived from about 75 to 100 mole percent dibasic acids containing 6 to 40 carbon atoms and 0 to about 25 mole percent modified dibasic acids, and

(2) by about 75～100% mole containing the dibasic alcohol of 2～10 carbon atoms, 0～about 25% mole modified dibasic alcohol and 0～about 25% mole be selected from aminoalcohol, diamine and lactam The repeating unit obtained by modifying the compound; the % mole is based on (1) being 100% mole and (2) being 100% mole;

(b) preparing an ethylene copolymer comprising ethylene and repeating units selected from the group consisting of acrylic acid, methacrylic acid, alkyl acrylates, alkyl methacrylates and comonomers of vinyl alcohol.

(c) drying the polyester and ethylene copolymer;

(d) forming a melt comprising from about 80 to about 99.9% by weight of dry polyester and from about 0.1 to about 20% by weight of dry ethylene copolymer;

(e) cooling the melt and forming solid particles;

(f) solid state polycondensation of the particles until a branched polyester having an intrinsic viscosity of at least about 0.70 is obtained;

(g) melting the branched polyester particles;

(h) adding a blowing agent to the branched polyester melt; and

(i) extruding the composition of step (h) through a die.

Detailed description of the invention:

It has been found that certain polymeric materials containing multiple hydroxyl groups, carboxylic acid groups or ester groups are used as branching agents for polyesters and polyesteramides to increase their melt viscosity and melt strength and improve foamability, Suitable polymeric materials include copolymers of ethylene with either acrylic acid, methacrylic acid, alkyl acrylates, alkyl methacrylates or vinyl alcohol monomers. The concentration of the ethylene copolymer branching agent is generally from about 0.1 to about 20% by weight of the total weight of the ethylene copolymer and polyester composition. The content of the ethylene copolymer is preferably 10% by weight or less.

The content of acrylic acid, methacrylic acid, alkyl acrylate and alkyl methacrylate monomers in the ethylene copolymer is generally about 0.5 to about 40% by weight, preferably less than 20% by weight, and the melting of such ethylene copolymers Body index values range from about 0.1 to about 200 grams/10 minutes (ASTM D-1238-56T). For ethylene copolymers containing alkyl acrylates or methacrylates, the alkyl group generally contains 1 to 4 carbon atoms.

For ethylene/vinyl alcohol copolymers, the vinyl alcohol content is from about 1 to about 95% by weight. The copolymers are readily prepared by hydrolyzing ethylene/vinyl acetate copolymers, desirably relatively low residual acetate groups (eg, less than about 1 or 2% by weight). The melt index of the copolymers generally ranges from about 0.1 to about 200 g/10 minutes.

Ethylene copolymers are typically stabilized with small amounts of antioxidants. For example, about 0.05 to about 0.1% by weight of Irganox (trade name) 1010, Irganox 1076, Ethanox (trade name) 330, etc. can be used. Additionally, small amounts of other stabilizers such as dilauryl thiodipropionate and Weston 619 may be used in combination with the stabilizers listed above.

A wide variety of polyester polymers can be used in the present invention, including polyesters derived from dibasic acids containing 6 to 40 carbon atoms and diols containing 2 to 10 carbon atoms. Typically, such polyesters have intrinsic viscosity (I.V.) values of from about 0.4 to about 0.70 (measured in a 60/40 phenol/tetrachloroethane solution) and are generally crystallizable. Such polyesters may be in any form including homopolymers, copolymers, modified polymers, branched polymers and blends.

Preferred dibasic acids for preparing polyesters include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, etc., or their alkyl esters. When naphthalene dicarboxylic acid is used, any isomer may be used, but preferred isomers include 2,6-, 2,7-, 1,5- and 1,6-isomers. Mixtures of the various isomers may also be used. Preferred isomers of cyclohexanedicarboxylic acid are the 1,3- or 1,4-isomers, which may be cis, trans isomers or a mixture of cis/trans isomers.

Preferred dihydric alcohols include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like. When cyclohexanedimethanol is used, it can be the 1,3- or 1,4-isomer, either cis, trans or a mixture of cis/trans isomers.

Polyester copolymers, ie, copolyesters, may contain up to about 25 mole percent of other dibasic acids or diols. Modified dibasic acids (in addition to those listed above) include oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, dimers, sulfoisophthalic acid, Or its metal salt etc. When any of the above-mentioned acids are listed, it goes without saying that the corresponding anhydrides, esters and acid chlorides are included. Modified diols (other than those listed above) include 1,6-hexanediol, neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and the like.

Polyesteramides may also be used in the practice of the present invention. Such polymers should contain the dibasic acid and diol moieties listed above. Additionally, the diol portion should contain up to about 25 mole percent of modifying compounds such as aminoalcohols, diamines and/or lactams. Some suitable compounds include materials such as 4-aminomethylcyclohexanemethanol, 1,6-hexanediamine, and caprolactam.

Polyesters, polyesteramides and ethylene copolymers in their various forms are readily prepared by conventional polymerization techniques well known in the art.

The combination of melt compounding and solid-state polycondensation can complete the branching reaction of ethylene copolymer and polyester to form branched polymerized polyester. Compared with polyester without polymer material branching, its melt viscosity and melt Body strength increased. The effect of branching is to significantly improve the foamability and blow molding properties of the polyester.

In a preferred process embodiment, the ethylene copolymer is dry blended with the polyester, dried in a vacuum or convection oven, and then melt compounded in the extruder at a temperature of from about 260°C to about 300°C. Optionally, the ethylene copolymer and polyester can be dried separately and fed to the extruder. The extrudate is formed into solid particles and dried. Particles of any shape may be used, including pellets, granules, powder or chips. Then, in a solid-phase polycondensation apparatus, a reaction is performed by circulating or blowing an inert gas such as nitrogen among the particles at about 200 to about 230°C. The solid state polycondensation reaction is carried out until the intrinsic viscosity value of the polymer blend reaches at least about 0.70 deciliter/gram, preferably reaches about 0.90 deciliter/gram,

The combination of melt compounding and solid-state polycondensation is used because the melt viscosity of branched polyesters increases significantly, which greatly limits the reaction of polymerizing high molecular weight polyesters in the melt phase. The resulting melt viscosity is such that the melt is difficult to handle. Additionally, in common extruders used for melt compounding, the reaction time is limited due to the size of the extruder. There is usually not enough time for a sufficient branching reaction to take place.

The resulting polymer is a ready to use branched polyester in a form convenient for processing into foam end products. Branched polyesters can be fed directly into the extruder, melted and mixed with blowing agents, or dry blended with other ingredients prior to melting to enhance the properties of the final product. Various end applications planned include the manufacture of films, tubes, blow molded items, extrusion coatings, food packaging containers and injection molded parts.

The melt viscosity of branched polyester at 280 ° C is above 500 Pa·s (5000 poise), and the melt strength is above -50%. These data are some unbranched polyesters such as polyethylene terephthalate Typical values for alcohol esters (PET). Preferably, the melt viscosity at 280°C is about 2,000 to 20,000 Pa·s (about 20,000 to 200,000 poise), and the melt strength is about -25 to +60%. Such a melt has excellent foaming properties. Both melt viscosity and melt strength were measured at 280°C.

Branched polyesters can be foamed by various methods including injecting an inert gas such as nitrogen or carbon dioxide into the melt during the extrusion or molding process. Inert hydrocarbon gases such as methane, ethane, propane, butane, and pentane, or chlorofluorocarbons, hydrochlorofluorocarbons, etc. may also be used. Other methods include dry blending an organic blowing agent with a branched polyester and then extruding or molding the composition to form a foamed article. During the extrusion or molding process, an inert gas such as nitrogen is extracted from the blowing agent to form a foaming effect. Typical blowing agents include azodicarbonamide, hydrazonocarbonamide, dinitrosopentamethylenetetramine, p-toluenesulfonylhydrazonodicarboxylate, 5-phenyl-3, 6-dihydro-1,3,4-oxadiazin-2-one, sodium borohydride, sodium bicarbonate, 5-phenyl tetrazole, p, p'-oxybis(benzenesulfonyl hydrazide), etc. . Still other methods include blending sodium carbonate or sodium bicarbonate with a portion of the branched polyester particles, blending an organic acid such as citric acid with another portion of the branched polyester particles, and then blending the blend of the two particles at high temperature extruded or molded. The carbon dioxide gas released by the interaction of sodium carbonate and citric acid plays a foaming role in the melt.

In particular, when ethylene copolymers of alkyl acrylates or methacrylates are used as branching agents, lower alkyl groups escape as volatile alcohols during foaming. This further enhances the desired foaming action.

Patents disclosing various foaming procedures and equipment include U.S. Patents 5,116,881, 5,134,028, 4,626,183, 5,128,383, 4,746,478, 5,110,844, 5,000,991, and 4,761,256. For other basic information about the foaming process, see Kirk-Othmer Encyclopedia of Chemical Technology, (Kirk-Othmer Encyclopedia of Chemical Technology), Third Edition, Volume 11, Pages 82-145 (1980), John Wiley and Sons Company, New York State New York, and Encyclopedia of Polymer Science and Engineering, Second Edition, Vol. II, pp. 434-446. (1985), John Wiley and Sons, New York, NY.

Many ingredients can be added to branched polyesters to enhance their properties, including buffers, antioxidants, metal inactivators, colorants, phosphorus-containing stabilizers, impact modifiers, nucleating agents, and UV and Heat stabilizers, etc. All of these additives and their use are well known in the art and need not be discussed further. Therefore, only a limited number are mentioned, and it goes without saying that any of these compounds can be used as long as they do not interfere with the properties of the branched polyester.

In many cases, nucleating agents such as talc, _TiO2 or small amounts of polyolefinic materials such as polyethylene, polypropylene, ethylene or propylene copolymers, etc. are useful additives to foamable branched polyester compositions. Certain nucleating agents play an important role in generating the location of the bubbles and affecting the cell size of the foamed sheet or foamed object.

Other desirable additives include impact modifiers and antioxidants. Examples of typical commercially available impact modifiers for use in the present invention that are well known in the art include ethylene/propylene terpolymers, styrene-based block copolymers, and various acrylic core/shell type impact modifiers. sex improver. The usual amount of impact modifier is 0.1-25% by weight of the composition, preferably 0.1-10% by weight of the composition. Examples of typical commercially available antioxidants useful in the present invention include, but are not limited to, hindered phenols, phosphites, diphosphites, polyphosphites, and mixtures thereof. Combinations of aromatic and aliphatic phosphite compounds may also be included.

The following examples, as typical of the present invention, further illustrate the present invention. All parts and percentages in the examples are by weight unless otherwise indicated. The materials and test procedures used for the results shown in the examples in this paper are as follows:

Intrinsic viscosity (I.V.) is measured at 25°C using a solution containing 0.50 g of polymer in 100 ml of a solvent consisting of 60% by weight phenol and 40% by weight tetrachloroethane.

Melt strength and die swell were determined according to ASTM D3835 at 280°C by passing molten polyester through a die with a diameter of 0.254 cm (0.1 inch) and a length of 0.635 cm (0.25 inch) at 20°C using an Instron rheometer. The shear rate of sec ^-1 is extruded downwards, and the extrudate falls freely. Die swell is determined by measuring the diameter of the extrudate as soon as it exits the orifice and dividing by the orifice diameter. Die swell is reported as percent die swell. Measure the diameter of the extrudate tip 15.24 centimeters (6 inches) long from the orifice of the die. Calculate the percent melt strength from the formula: $\frac{\mathrm{D.}-0.254}{0.254}\×100$

where: D is the diameter in centimeters of the extrudate supporting an extrudate length of 15.24 centimeters (6 inches). If D is less than 0.254 cm (0.1 inch), the melt strength is negative because the diameter of the extrudate does not increase. If D is greater than 0.254 cm (0.1 inch), the unmelt strength is positive.

Melt viscosity is measured at zero shear at 280°C according to ASTM D4440.

The mole percents of residual diol and acid are measured by gas chromatography or NMR.

Example 1

Dry pellets of polyethylene terephthalate (PET) (I.V.0.60), ethylene/vinyl alcohol copolymer (EVOH) (ethylene content 32% by weight, melt index 0.7) were mixed in a stainless steel vessel. The dry pellets and talc were mixed thoroughly to form a blend containing 5% by weight EVOH and 0.5% by weight talc. The pellet blend was fed to the extruder and melt mixed at 275°C. The melt was extruded through a rod die and the rod was cut into 0.3175 cm (1/8 inch) pellets. These dry pellets were then subjected to solid state polycondensation conditions in a 3.175 cm (1.25 inch) diameter glass column. The glass column was jacketed for solvent reflux, so the column was heated. Use ethylene glycol to reflux and maintain the column temperature at 198°C. The bottom of the column has a porous glass surface that allows inert gas to pass upward through the column. Nitrogen gas was passed through the polymer pellets at a rate of 4 ft3/hr to expel ethylene glycol and other volatile components that were gradually formed as the intrinsic viscosity of the polymer increased. Within 18 hours, the intrinsic viscosity of the polymer sample reached 0.81. The sample had a melt strength of -16.5%, a die swell of +29.5%, and a melt viscosity of 5,800 Pa.s (58,000 poise) at 280°C. The starting poly(ethylene terephthalate) sample had a melt strength of -105%, a die swell of -30%, and a melt viscosity of 500 (Pa·s) at 280°C (5,000 poise).

A large number of branched polyesters similar to those described above are produced in a solid state polycondensation unit scaled up appropriately.

A sample of the blend that had been converted to a branched polyester was fed to a series of extruders consisting of the following machines and components capable of injecting a gaseous blowing agent at high pressure into the polymer melt , 5.08 cm (2 inches) first extruder, capable of decompressing and foaming the melt, 6.35 cm (2.5 inches) second extruder, an annular die at the end of the first extruder through which the extrudate passes Head [7.62 cm (3 inches) in diameter]. The two extruders are connected by what is known as a low pressure overlap. The gaseous blowing agent used was isopentane. The extruder, overlap zone and annular die were heated at 260°C and 274°C throughout the length as detailed below:

5.08 cm (2 inches) first extruder =260°C

Overlapping area =260℃

6.35 cm (2.5 inches) second extruder = 260°C

7.62 cm (3 inches) ring die =274°C

Other extrusion conditions and parameters are as follows:

Pressure (psi)

5.08 cm (2 inches) extruder 5600～6000

Overlapping area 3740～3860

6.35 cm (2.5 inches) extruder 2210～2230

Isopentane injection 3250～5600

extrusion speed

5.08 cm (2 inches) extruder 87 rpm

6.35 cm (2.5 inches) extruder 16.4 rpm

Polymer extrusion capacity 29.937 kg (66 lbs)/hour

Injection amount of isopentane 0.726 kg (1.6 lb)/hour

Under these conditions, the branched PET composition described above is extruded to have the desirable properties for producing good foams. Foams produced from annular dies are dry to the touch and have good melt strength, so they can be stretched easily when passed through water-cooled mandrels. The foam was slit and collected in sheets 0.9144 meters (36 inches) wide.

Foam thickness and density are largely controlled by changes in line speed and isopentane level. The resulting foam had a thickness of 59 mils, an I.V. of 0.80, a crystallinity of 15.3% as determined by differential scanning calorimetry (DSC), and a density of 0.21 g/cm. Scanning electron microscopy and confocal optical microscopy showed that the cell structure was well formed, all cells were closed, and the diameter was 100-200 microns. The foam has the following excellent post-foaming properties:

(a) A small piece of styrofoam produced above was immersed in boiling water for 2 minutes and allowed to cool at room temperature. The thickness of the foam surface was measured at several places with a FOWLER micrometer, and the average thickness was 91 mils, which produced a 54% increase in the thickness of the foam. The density of this post-expanded foam was measured to be 0.11 g/ ^cm3 . The crystallinity determined by DSC was 31.26%. Scanning electron microscopy and confocal optical microscopy showed that the cell structure was well formed, all cells were closed, and the diameter was 200-400 microns.

(b) A small piece of foam was also post-foamed in a conventional air oven at 175°C for 3 minutes. The foam had an average thickness of 75 mils and a density of 0.16 g/ ^cm3 . The crystallinity determined by DSC was 31.53%. Scanning electron microscopy and confocal optical microscopy showed that the cell structure was well formed, all cells were closed, and the diameter was 200-300 microns.

The above example is improved as follows, and good foaming results are also obtained:

(a) The PET/EVOH blends used contain 0.3%, 1%, 3% and 5% (by weight) of EVOH copolymers, respectively;

(b) Use nitrogen or carbon dioxide instead of isopentane as blowing agent;

(c) Before the extrusion process, 2% (weight) chemical blowing agent azodicarbonamide is sprinkled on the branched PET to replace the isopentane blowing agent;

(d) Combination of chemical blowing agent and gas blowing agent, that is, before the extrusion process, 0.5% (weight) chemical blowing agent azodicarbonamide is sprinkled on the branched PET, and then extruded as above Use isopentane blowing agent during out.

Likewise, good results were obtained using 5% by weight of ethylene/acrylic acid copolymer (CAS No. 9010-77-9) containing 8% by weight of acrylic acid instead of EVOH copolymer.

Example 2

A branched poly(ethylene terephthalate) polyester (IV 0.68) containing 0.3 mole % trimellitic anhydride, 1% by weight of the EVOH copolymer of Example 1 and 0.5% ( weight) TiO ₂ , repeat the steps of Example 1. The produced foamed plastic feels dry and has a good cell structure. Likewise, when foaming poly(ethylene terephthalate) copolyesters branched with copolymers of EVOH containing 0.2 mole % trimellitic acid or pyromellitic dianhydride , also obtained good results.

Example 3

Using poly(ethylene terephthalate) copolyester (1.V.0.69) containing 3.5% by mole of 1,4-cyclohexanedimethanol, 5% by weight EVOH copolymer (95% by weight ) ethylene, melt index 4.2), 1.0% (weight) sodium carbonate and 0.5% (weight) talcum, repeat the step of example 1. The foamed plastics produced feel dry and have a good and uniform cell structure.

Example 4

Using poly(1,4-cyclohexylene dimethylene terephthalate) (I.V.0.68), 3% by weight ethylene/methyl acrylate copolymer (20% by weight) methyl acrylate, melt Index 6.0) and 1% (weight) talc, repeat the steps of Example 1. The foam produced is dry to the touch and has a good and uniform cell structure. Good results were likewise obtained when 0.5% by weight of ethylene/methyl acrylate copolymer was used.

Example 5

Using poly(ethylene terephthalate) copolyester (IV0.55) containing 9 mol% 1,4-cyclohexanedimethanol, 2% by weight ethylene/methyl methacrylate copolymer (15 % (weight) methyl methacrylate, melt index 10.1) and 0.5% (weight) TiO ₂ , repeat the steps of Example 1. The foamed plastic produced is dry to the touch and has a good and uniform cell structure. Good results were also obtained with poly(ethylene terephthalate) copolyester (IV 0.65) containing 17 mole % diethylene glycol.

Example 6

Using poly(1,4-cyclohexylene dimethylene terephthalate) copolyester (IV0.68) containing 15% by mole of ethylene glycol, 1% by weight of ethylene/acrylic acid copolymer (88 % (weight) ethylene, melt index 7.2), 0.5% (weight) sodium carbonate and 0.5% (weight) TiO ₂ , repeat the steps of Example 1. The foamed plastic produced is dry to the touch and has a good and uniform cell structure. Likewise, when using a copolymer (IV0.69) of poly(1,4-cyclohexylene dimethylene terephthalate) containing 5 mole percent isophthalic acid, containing 17 mole percent isophthalic acid When using the copolymer (IV0.67) or the copolymer (IV0.65) containing 10 mole % 2,6-naphthalene dicarboxylic acid, and when using poly( Good results were also obtained with copolyamide esters of ethylene terephthalate).

Example 7

Example 1 was repeated using polyethylene 2,6-naphthalate (I.V.0.68), 5% by weight EVOH copolymer (90% by weight ethylene, melt index 1.3) and 2% by weight talc A step of. The foamed plastic produced is dry to the touch and has a good and uniform cell structure. Likewise, good foaming results were obtained when 2% by weight of the chemical blowing agent azodicarbonamide was sprinkled on the branched polyester prior to the extrusion process in place of the isopentane blowing agent used.

The present invention has been described in detail with particular preferred embodiments of the present invention, but it goes without saying that modifications and improvements can be made within the spirit and scope of the present invention.

Claims (32)

1. A limiting viscosity be at least 0.7 deciliter/gram, melt viscosity be high enough to can extrude or molding process in the foaming product of the branched polyester that foams, described branched polyester is to make by the composition that melt compounded and solid phase polycondensation one must comprise following component:

   (A) (A) and (B) polyester of 80～99.9% weight of gross weight, this polyester comprises:

   (1) repeating unit that obtains by the modification diprotic acid of 75～100% moles of diprotic acid that contain 6～40 carbon atoms and 0～25% mole and

   (2) by 75～100% moles of dibasic alcohol that contain 2～10 carbon atoms, 0～25% mole of modification dibasic alcohol and 0～25% mole are selected from the repeating unit that the modified compound of amino alcohol, diamines and lactan obtains; Described % mole is 100% mole in (1) and is 100% mole in (2); With

   (B) (A) and (B) the containing that ethene constitutes and be selected from the ethylene copolymer of the repeating unit that vinylformic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate and vinyl alcohol monomer constitute of 0.1～20% (weight) of gross weight.
2. 2. the foaming product of claim 1 narration, wherein the diprotic acid of polyester is selected from terephthalic acid, m-phthalic acid, naphthalic acid, cyclohexane dicarboxylic acid and alkyl ester and composition thereof.
3. 3. the foaming product of claim 2 narration, wherein naphthalic acid is selected from 2,6-, 2,7-, 1,5-and 1,6-naphthalic acid isomer and composition thereof.
4. 4. the foaming product of claim 2 narration, wherein cyclohexane dicarboxylic acid is selected from 1,3-, 1,4-, suitable-and anti--cyclohexane dicarboxylic acid isomer and composition thereof.
5. 5. the foaming product of claim 1 narration, wherein the dibasic alcohol of polyester is selected from ethylene glycol, 1,4-butyleneglycol and 1,4-cyclohexanedimethanol.
6. 6. the foaming product of claim 1 narration, wherein the modification diprotic acid of polyester is selected from terephthalic acid, m-phthalic acid, naphthalic acid, cyclohexane dicarboxylic acid, oxalic acid, Succinic Acid, pentanedioic acid, hexanodioic acid, sebacic acid, suberic acid, dipolymer acid, sulfoisophthalic acid and composition thereof.
7. 7. the foaming product of claim 1 narration, wherein the modification dibasic alcohol of polyester is selected from ethylene glycol, 1,4-butyleneglycol, 1,4 cyclohexane dimethanol, 1,6-hexylene glycol, neopentyl glycol, 2,2,4,4-tetramethyl--1,3-cyclobutanediol and composition thereof.
8. 8. the foaming product of claim 1 narration, wherein the modified compound of polyester is selected from 4-aminomethyl cyclohexane methanol, 1,6-hexanediamine and hexanolactam.
9. 9. the foaming product of claim 1 narration, wherein branched polyester contains the following ethylene copolymer of 10% (weight).
10. 10. the foaming product of claim 1 narration, the therein ethylene multipolymer contains the comonomer that is selected from vinylformic acid, methacrylic acid, alkyl acrylate and alkyl methacrylate of 0.5～40% (weight).
11. 11. the foaming product of claim 10 narration, therein ethylene multipolymer contain the following comonomer of 20% (weight).
12. 12. the foaming product of claim 1 narration, the therein ethylene multipolymer contains the vinyl alcohol of 1～95% (weight).
13. 13. the foaming product of claim 12 narration, therein ethylene/multipolymer is by ethylene/vinyl acetate copolymer hydrolysis preparation, and acetic ester residue content is less than 1～2%.
14. 14. the foaming product of claim 1 narration, wherein alkyl acrylate and alkyl methacrylate contain the alkyl of 1～4 carbon atom.
15. 15. the foaming product of claim 1 narration, the therein ethylene multipolymer is stable with adding oxidation inhibitor.
16. 16. the foaming product of claim 1 narration, wherein polyester also comprises the monomer branching agent.
17. 17. method for preparing the branched polyester foaming product that comprises following operation:

    (a) preparation comprises the polyester of repeating unit (1) and (2):

    (1) repeating unit that obtains by the modification diprotic acid of 75～100% moles of diprotic acid that contain 6～40 carbon atoms and 0～25% mole and

    (2) by 75～100% moles of dibasic alcohol that contain 2～10 carbon atoms, 0～25% mole of modification dibasic alcohol and 0～25% mole are selected from the repeating unit that the modified compound of amino alcohol, diamines and lactan obtains; Described % mole is 100% mole in (1) and is 100% mole in (2);

    (b) preparation comprises that ethene constitutes and is selected from vinylformic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate and the vinyl alcohol copolymer ethylene copolymer with the repeating unit of monomer formation;

    (c) with this polyester and ethylene copolymer drying;

    (d) form a kind of melt of dry ethylene copolymer of the dry polyester and 0.1～20% (weight) that comprises 80～99.9% (weight);

    (e) with the cooling of this melt and make solid particulate;

    (f) make the particle solid phase polycondensation, until obtaining the branched polyester of limiting viscosity at least 0.70;

    (g) make the branched polyester particle fusion;

    (h) whipping agent is added in the branched polyester melt; With

    (i) composition of operation (h) is extruded through die head.
18. 18. the method for claim 17 narration, wherein operation (a) polyester prepares with the diprotic acid that is selected from terephthalic acid, m-phthalic acid, naphthalic acid, cyclohexane dicarboxylic acid and alkyl ester and composition thereof.
19. 19. the method for claim 18 narration, wherein operation (a) polyester is with being selected from 2,6-, 2,7-, 1,5-and 1, the naphthalic acid preparation of 6-naphthalic acid isomer and composition thereof.
20. 20. the method for claim 18 narration, wherein operation (a) polyester is with being selected from 1,3-, 1,4-, suitable-and the cyclohexane dicarboxylic acid of anti--cyclohexane dicarboxylic acid isomer and composition thereof prepare.
21. 21. the method for claim 17 narration, wherein operation (a) polyester is with being selected from ethylene glycol, 1, the dibasic alcohol preparation of 4-butyleneglycol and 1,4 cyclohexane dimethanol.
22. 22. the method for claim 17 narration, wherein operation (a) polyester prepares with the modification diprotic acid that is selected from terephthalic acid, m-phthalic acid, naphthalic acid, cyclohexane dicarboxylic acid, oxalic acid, Succinic Acid, pentanedioic acid, hexanodioic acid, sebacic acid, suberic acid, dipolymer acid, sulfoisophthalic acid and composition thereof.
23. 23. the method for claim 17 narration, wherein operation (a) polyester is with being selected from ethylene glycol, 1,4-butyleneglycol, 1,4-cyclohexanedimethanol, 1,6-hexylene glycol, neopentyl glycol, 2,2,4,4-tetramethyl--1, the modification dibasic alcohol preparation of 3-cyclobutanediol and composition thereof.
24. 24. the method for claim 17 narration, wherein operation (a) polyester is with being selected from 4-aminomethyl cyclohexane methanol, 1, the modified compound preparation of 6-hexanediamine and hexanolactam.
25. 25. the method for claim 17 narration, wherein the ethylene copolymer of operation (b) preparation contains the comonomer that is selected from vinylformic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate of 0.5～40% (weight).
26. 26. the method for claim 25 narration, wherein the ethylene copolymer of operation (b) preparation contains the following comonomer of 20% (weight).
27. 27. the method for claim 17 narration, wherein the ethylene copolymer of operation (b) preparation contains the vinyl alcohol of 1～95% (weight).
28. 28. the method for claim 17 narration, wherein operation (b) ethylene copolymer prepares with alkyl acrylate and alkyl methacrylate, and alkyl wherein contains 1～4 carbon atom.
29. 29. the method for claim 17 narration, wherein the melt of operation (d) formation comprises the following ethylene copolymer of 10% (weight).
30. 30. the method for claim 17 narration, wherein operation (f) solid phase polycondensation proceeds to the branched polyester limiting viscosity and is at least 0.90.
31. 31. the method for claim 17 narration, wherein the melt viscosity of the branched polyester that is melted of operation (g) is 500 handkerchiefs more than second, and melt strength be more than-50%, and both are all 280 ℃ of mensuration down.
32. 32. the method for claim 31 narration, wherein the branched polyester that is melted in the operation (g) is that 2000～20,000 handkerchief second, melt strength are-25% to+60% 280 ℃ of following melt viscosities, and both are all 280 ℃ of mensuration.